Purpose: :
Retinal screenings for diabetic retinopathy via digitalphotography are becoming more common in a variety of clinicalsettings. Protocols for these screenings differ, but most involvesome type of visual acuity measurement. The Vanderbilt OphthalmicImaging Center assesses visual acuity with the Optec 800, aportable, inexpensive instrument comprised of a reduced, illuminatedETDRS chart. The present study tests the validity of the portableOptec instrument against the full–size, illuminated EarlyTreatment of Diabetic Retinopathy Study (ETDRS) chart.

Methods: :
Using a prospective design, data from 37 patients (72eyes) were evaluated. The following data were recorded for eachpatient: age, gender, ocular history, presence and type of refractivecorrection. Patients were randomized, performing either theETDRS or Optec 800 test first, while always starting the testwith the right eye. Patients were instructed to read each letterindividually until an entire line of letters had been incorrectlyidentified. Performance was recorded using single letter scoring,and a total correct score was calculated for each eye on eachtest.

Results: :
There was no statistically significant difference inperformance between the Optec 800 and the illuminated ETDRS(P=0.09). The average of differences was –1.2, indicatingthat patients missed approximately 1.2 more letters on the Optec800 versus the ETDRS, which is not clinically relevant. Additionalfactors such as gender, age, and test performed first did notaffect performance between the two methods. No statisticallysignificant adaptation or fatigue trend was found between righteye (tested first) and left eye.

Conclusions: :
There is no difference in performance between theOptec 800 vision screener and the illuminated ETDRS chart forour sample size. The study indicates that the Optec 800 instrumentprovides a similar visual acuity measurement as compared withthe ETDRS chart, and therfore the Optec 800 may prove usefulfor other screening protocols.